1. Field of the Invention
The invention relates to a method of controlling access to a time-division multiplex message transmission path to which a central unit and a plurality of subscribers are connected and on which the central unit produces cyclically recurring frames of a predetermined number of words each having a predetermined number of bits, at least one signaling word being assigned to each frame. A variable, contiguous portion of the said number of words is allocated to narrow-band channels through each of which a word is transmitted in each frame, and a further variable, contiguous portion of the said number of words is reserved for the forming of a high-rate channel through which data packets are transmitted during each sequence of consecutive words.
2. Description of the Prior Art
Such a method is disclosed in U.S. Pat. No. 4,154,983, in which a ring transmission path is used, the selection of the subscribers to be interconnected in the narrow-band channels being effected by signalling information in the signal words of successive frames. The partition between the narrow-band channels and the high-rate channel is formed by a predetermined marker bit assigned to each data word, which bit gets a different value at the end of the narrow-band channels. Controlling the access to the high-rate channel by a subscriber is in essence effected by the central unit. Consequently the central control unit must perform a plurality of control functions so that the control unit is complicated and bulky.
It is an object of the invention to provide a method of the type described in the opening paragraph, which has a variable partition between the narrow-band channels and the high-rate channel, access to the high-rate channel entirely being controlled by the subscribers without assistance from the central unit.